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Candidatus Liberibacter solanacearum haplotype B (CLsoB) is an economically important pathogen of tomato (Solanum lycopersicum L.) crops in New Zealand and Central and North America. Currently, resistant cultivars of tomato are not available as a management tactic because breeding programmes lack sources of resistance. Therefore, the objective of this study was to identify sources of resistance in tomato to CLsoB. Forty‐six landraces of tomato were collected from several states in Mexico and were inoculated with CLsoB using 20 infested adults of Bactericera cockerelli per plant. Two assays were done over two years under greenhouse conditions. In the first trial, landraces FC22 and FC44 showed a significantly higher proportion of resistant plants, less symptom severity and longer incubation time compared with the other forty‐four landraces and two susceptible cultivars. In the second assay, resistance to CLsoB of the landraces FC22 and FC44 was confirmed because they had again significantly greater numbers of resistant plants, less symptom severity, relative lower CLsoB titers and longer incubation time relative to the other genotypes. All plants considered resistant from both assays had DNA of CLsoB. Results indicate that all resistant plants from these landraces are promising sources for the development of tomato cultivars with resistance to CLsoB. [ABSTRACT FROM AUTHOR]

A new case of Fusarium oxysporum (Fo) causing significant economic losses in pepper (Capsicum annuum) crops in Culiacan, Mexico was recently reported. To fight this newly discovered disease, it was necessary to analyze the host specificity to use this information in an integrated disease management. To achieve that, the host range of 10 strains of Fo collected from diseased pepper plants was checked on the following species: Capsicum annuum, Solanum lycopersicum, Nicotiana tabacum, Nicotiana bethamiana, Solanum melongenea, Phisalis ixocarpa, Cucurbita pepo, Cucumis sativus, Cucumis melo. These 10 strains were also tested on four differential tomato cultivars for Fo f. sp. lycopersici (Fol) races identification. Both assays were repeated twice under growth-chamber conditions. All 10 strains of Fo caused wilting symptoms on each of the species mentioned above, indicating that these strains have a wide host range. During race characterization assays, the typical phenotypic responses displayed by the four differentials 'Bony Best', 'Manapal', 'Walter' and 'I3R3' against these 10 strains, suggested that all these strains belong to Fol race 2 (Fol-2). These strains were tested by using PCR technique to detect the SIX genes specific for Fol races and the results indicated also that these strains belong to Fol-2. However, further molecular and vegetative compatibility group studies with these strains most be carry out to corroborate these results. To our knowledge, this is the first cross pathogenicity report of Fo in Solanaceae and Cucurbitaceae crops in Mexico. [ABSTRACT FROM AUTHOR]

Fusarium species cause macular diseases in the maize that induce rotting of stems, roots and grains of corn and finally the death of the plant. In the present study, the presence and diversity of Fusarium species associated with these damages in Sinaloa was molecularly identified. During the sowing periods in the years 2013-2014, stem and root tissue from young and adult plants, as well as diseased pod kernels, was collected in the municipalities of Ahome, Culiacan and Elota in the state of Sinaloa. In this investigation, species F. verticillioides, F. oxysporum, F. subglutinans, F. equiseti, F. nygamai, F. cf. bullatum and F. andiyazi, were identified by enzymatic sequencing analysis, where F. verticilloides was the most predominant species. Likewise, the presence in Mexico of Fusarium cf. bullatum causing damage to corn. [ABSTRACT FROM AUTHOR]

A new disease on greenhouse pepper (Capsicum annuum L.) plants in Culiacan, Mexico with symptoms of chlorosis, wilting and vascular necrosis was observed in 2014. Sixty diseased pepper plants were collected from three different areas of the Culiacan Valley to determine the causal agent of the disease and analyse the potential risk presented by this disease in this region. Fusarium oxysporum was recovered consistently (88% of samples collected) and identified based on cultural, morphological and pathogenicity tests, as well as by PCR amplification and DNA sequencing of the TEF-1α gene. Two pathogenicity tests with 10 monoconidial isolates of F. oxysporum, which were selected randomly from diseased tissues, produced disease symptoms similar to those observed on pepper plants in the greenhouses. Symptoms were different from the typical root rot, wilting and necrosis caused by F. solani and F. oxysporum f. sp. radicis-capsici and instead matched those reported for F. oxysporum f. sp. capsici causing pepper wilt. The results suggest that the causal agent of pepper wilt in the samples analysed was F. oxysporum. This is the first report of pepper wilt caused by this fungus in Mexico, and this disease is a potential threat for pepper production in this region. [ABSTRACT FROM AUTHOR]

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Mexico, the center of origin of maize (Zea mays L.), has taken actions to preserve the identity and diversity of maize landraces and wild relatives. Historically, spatial isolation has been used in seed production to maintain seed purity. Spatial isolation can also be a key component for a strategy to minimize pollen-mediated gene flow in Mexico between transgenic maize and sexually compatible plants of maize conventional hybrids, landraces, and wild relatives. The objective of this research was to generate field maize-to-maize outcrossing data to help guide coexistence discussions in Mexico. In this study, outcrossing rates were determined and modeled from eight locations in six northern states, which represent the most economically important areas for the cultivation of hybrid maize in Mexico. At each site, pollen source plots were planted with a yellow-kernel maize hybrid and surrounded by plots with a white-kernel conventional maize hybrid (pollen recipient) of the same maturity. Outcrossing rates were then quantified by assessing the number of yellow kernels harvested from white-kernel hybrid plots. The highest outcrossing values were observed near the pollen source (12.9% at 1 m distance). The outcrossing levels declined sharply to 4.6, 2.7, 1.4, 1.0, 0.9, 0.5, and 0.5% as the distance from the pollen source increased to 2, 4, 8, 12, 16, 20, and 25 m, respectively. At distances beyond 20 m outcrossing values at all locations were below 1%. These trends are consistent with studies conducted in other world regions. The results suggest that coexistence measures that have been implemented in other geographies, such as spatial isolation, would be successful in Mexico to minimize transgenic maize pollen flow to conventional maize hybrids, landraces and wild relatives. [ABSTRACT FROM AUTHOR]